GB/T 40792-2021Test method of weight loss of sintered neodymium iron boron permanent magnets (English PDF)
烧结钕铁硼永磁体失重试验方法
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Issued by
SAMR; SAC
Level / Type
National · Recommended
Issue date
October 11, 2021
Implementation date
May 1, 2022
Scope
GB/T 40792-2021 is the English-translated version of 烧结钕铁硼永磁体失重试验方法.
GB/T 40792-2021 is a test method for the weight loss of sintered NdFeB (neodymium iron boron) permanent magnets exposed to high temperature, high pressure water vapour.
A sample that has been accurately weighed and measured is placed in a high-pressure vessel, where the vapour reacts with the surface grains so that they detach and the surface layer corrodes and turns to powder; after a set test period the sample is taken out.
Weight loss is defined as the mass lost through corrosion per unit area of the magnetic orientation surface, the face perpendicular to the easy magnetization direction, and is expressed in milligrams per square centimetre.
The method serves to evaluate the corrosion resistance of these magnets, including blanks, semi-finished and finished products. It was issued on 11 October 2021 and has applied since 1 May 2022.
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Document preview — GB/T 40792-2021
National Standard of the People's Republic of China
- ICS
- 77.120.99
- Classification
- H 14
Issued by: State Administration for Market Regulation; Standardization Administration of the PRC
Contents
- Foreword
- 1 Scope
- 2 Normative references
- 3 Terms and definitions
- 4 Method summary
Foreword
This document is in accordance with the provisions of GB/T 1.1-2020 "Guidelines for Standardization Work Part 1: Structure and Drafting Rules of Standardization Documents" Drafting.
1 Scope
This document specifies the weight loss test method for sintered NdFeB permanent magnets under high temperature, high pressure, and water vapor environmental conditions.
This document is suitable for evaluating the corrosion resistance of sintered NdFeB permanent magnets under high temperature, high pressure, and water vapor environmental conditions.
2 Normative references
The contents of the following documents constitute the indispensable clauses of this document through normative references in the text. Among them, dated quotations Only the version corresponding to that date is applicable to this document; for undated reference documents, the latest version (including all amendments) is applicable to this document.
GB/T 626-2006 Chemical reagent nitric acid
GB/T 678 Chemical reagent ethanol (anhydrous ethanol)
GB/T 8170 Numerical rounding rules and the expression and determination of limit values
3 Terms and definitions
The following terms and definitions apply to this document.
3.1 Sintered neodymium iron boron permanent magnet
A block sintered neodymium iron boron permanent magnet material with a certain geometric shape.
Note: Including sintered NdFeB permanent magnet blanks, semi-finished products and finished products.
3.2 Magnetic orientation surface
Regularly shaped anisotropic permanent magnets whose surfaces are perpendicular to the easy magnetization direction or irregularly shaped permanent magnets are processed into regular shapes The surface perpendicular to the opposite direction of easy magnetization after the sample.
Note 1. Permanent magnets have regular shapes such as squares, columns, rings, etc.; irregular shapes such as tile-shaped, etc.
Note 2. The magnetization orientation direction is the easy magnetization direction of the magnet.
3.3 Weight loss (WL)
The sintered neodymium iron boron permanent magnet sample is exposed to high temperature and high pressure water vapor environmental conditions, and the surface area per unit magnetic orientation surface is paired due to corrosion. Should the quality loss.
Note: The unit of weight loss is milligrams per square centimeter (mg/cm²).
4 Method summary
Put the sintered neodymium iron boron permanent magnet sample that has been accurately weighed and dimensioned into a high-pressure container, and the sample is evaporated in high-temperature and high-pressure water. Under the action of gas, the surface grains react with water vapor, causing the grains to peel off and the surface layer to corrode and pulverize. After continuing the test for a certain period of time, take out the test […]
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This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 15 pages — is available in the English PDF.
Referenced standards
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Related Standards
GB/T 626-2006 — Chemical reagent -- Nitric acid
GB/T 678-2023 — Chemical reagent - Ethanol
GB/T 8170-2008 — Rules of rounding off for numerical values & expression and judgement of limiting values
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